1. Field of the Invention
This invention relates to a synchronizing signal separation device which separates a synchronizing signal from an input signal which includes the synchronizing signal.
2. Description of the Prior Art
A conventional synchronizing signal separation device for separating a synchronizing signal from a signal, such as a video signal, to which the synchronizing signal is added, is configured as shown in FIG. 1.
FIG. 1 is a diagram showing the configuration of a conventional synchronizing signal separation device. In FIG. 1, a video signal is input to input terminal 1. The front end of a synchronizing-signal portion in the video signal is clamped by a peak clamp circuit 2 to a preset clamp level, as represented by "a" in FIG. 2. The video signal is then supplied to a comparator 3, which provides a synchronizing signal as represented by d in FIG. 2 by comparing the supplied video signal with a slice level set to a more or less higher level than the clamp level, and outputs the synchronizing signal from output terminal 4.
However, in a video cassette recorder, a still-picture video system or the like, which records a video signal on a recording medium, such as a magnetic tape, a magnetic disk or the like, and reproduces the video signal recorded on the recording medium, an overshoot as represented by b in FIG. 2 or a smear as represented by c in FIG. 2 is produced in the synchronizing signal due to emphasizing or deemphasizing processing performed when recording or reproducing the video signal, deteriorating the waveform of the signal. As a result, the synchronizing signal output from the output terminal 4 shown in FIG. 1 becomes as represented by e or f in FIG. 2.
That is, if an overshoot is produced in the waveform of the synchronizing signal, as represented by b in FIG. 2, the rise time of the waveform of the synchronizing signal separated by the synchronizing signal separation device shown in FIG. 1 starts earlier than the original rise time. If a smear is produced in the waveform of the synchronizing signal, as represented by c in FIG. 2, the fall time of the waveform of the synchronizing signal separated by the synchronizing signal separation device shown in FIG. 1 becomes later than the original fall time. Hence, it is difficult to provide an exact synchronizing signal.